Artificial joint is a kind of artifacts implanted into human body to replace natural human knee joint that becomes dysfunctional due to accidental injury, impairment or degeneration on account of fatigue, skeletal variations. There are various types of artificial joints, one of which is artificial hinge joint. Artificial hinge joint has been utilized since 1940s as an implant being implanted into human body to heal diseases such as bone defect or soft tissue dysfunctional.
A prior artificial hinge joint in the early years simply comprises a hinge component and a fixed bone shank, and has short service life. Since 1970s, the second generation of artificial hinge joint is made axially rotatable and used metal or polyethylene as bearing interface, which helps lengthen the service life of artificial joint. Since 1980s, the third generation of modularized artificial hinge joint has been developed by Stryker which further improves clinical effectiveness. However, since the third generation of artificial hinge joint still utilized hinge for transferring force in a way similar to the two previous generations, fracture problem still exists, in which plastic components near the hinge is still often easily broken and thus needs replacement.
Since 2000, some artificial joint manufacturers such as Zimmer Company (U.S. Pat. No. 6,773,461) revealed an artificial joint which reduces the bearing force of the hinge and further reduces the damage rate of plastic components. Moreover, since in this design, the axially rotatable hinge post combines with the hinge acting as a pivot during the implantation, the implant surgery can thus be performed in a less invasive way. However, in the above-mentioned model, the hinge post includes a screw thread parallel to the rotational direction of the artificial joint, causing the potential risk of the hinge post coining loose and falling off from the joint, which further causes the artificial joint to become ineffective.